JPH08238849A - Image forming medium - Google Patents

Abstract

PURPOSE: To provide an image forming medium which is good in image density, excellent in green storage stability, and excellent in inhibition of YAKIDASHI (discoloration) owing to fog and light, and an image forming method using that. CONSTITUTION: An image is formed by heating in an image shape or image exposure and heating of an image forming medium which contains at least organic silver salt, a reducing agent, and a pyridazine thionic derivative in a recording layer on a base material, or an image forming medium which contains further photosensitive silver halide or a photosensitive silver halide- forming agent in the recording layer, and the image forming medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image medium on which an image is formed by a redox reaction, an image forming method using the image forming medium and an image forming method.

[0002]

2. Description of the Related Art Recently, various recording materials have been researched and developed for practical use in the fields of information recording, medical field, etc., in response to social demands such as diversification and increase of information, resource saving and pollution-free. Has been done. Among them, the heat-sensitive recording material has the following advantages: (1) a monochrome image is recorded by simply heating it, and a complicated developing process is unnecessary;
It is widely used because it can be manufactured using a compact device and (3) maintenance costs are low.

However, in the thermal recording system using the thermal head, the structure of the thermal head limits the high-speed control of heating / cooling of the heating element and the densification of the heating element. Recording and high quality recording were difficult.

In order to solve this drawback, it has been proposed to carry out thermal recording at a high speed and a high density in a non-contact manner with a thermal recording material by using a laser beam (for example,
JP-A-50-23617, JP-A-54-1211
40, JP-A-57-11090, JP-A-5
8-94494, JP-A-62-56195, etc.). However, since the thermosensitive coloring layer generally does not easily absorb light in the visible and near-infrared regions, there is a problem that heat energy required for coloring cannot be obtained unless the laser output is considerably increased.

On the other hand, as a method capable of high-speed recording, high-density recording, and high-quality recording even with a low-output laser, Japanese Patent Publication Nos. 43-4921 and 43-4924,
JP-B-44-26582 and JP-A-46-607.
A method of forming an image by optical writing and thermal development disclosed in Japanese Patent No. 4 is known. This image forming method uses a photosensitive silver halide in a catalytic amount and a non-photosensitive organic silver salt as an image forming material. Further, Japanese Patent Application Laid-Open No. 48-97523 describes a method of forming an image by giving a heat-developable light-sensitive material containing no silver halide to heat it so as to activate the heat-developable light-sensitive material. .

The heat-developable photoconductor using an organic silver salt is a technique which has been attracting attention in recent years because it requires no wet treatment unlike the conventionally known silver halide photographic method. In this, an oxidation-reduction reaction is caused in the exposed area and heating to form an image. The latent image on the silver halide serves as a catalyst, and the organic silver salt reacts with the reducing agent under heating to form an image. It is known to add a toning agent to control the color appearance of the image area. The toning agent also has a function as a development promoting portion and is an essential component when a weak reducing agent is used.

However, there is a problem in that the effect of the color toning agent is lost over time, and the image density and photosensitivity after storage are lowered. In contrast, US Pat. No. 3,446,648 proposes a method using an acylated phthalazinone. However, the above-described color tone shows its effect with time when stored at room temperature or higher and under humid conditions, but the initial color tone effect is not sufficient, and the transparency of the photoreceptor after time is poor. , And inferior homogeneity of the image area.

An object of the present invention is to eliminate the above problems and to provide a photoreceptor having a high image density and excellent homogeneity, a low fog density and an excellent suppression of printing by light.

The heat-developable photoconductor using an organic silver salt is a technique which has been drawing attention in recent years because it requires no wet treatment unlike the conventionally known halogenated photographic method. In this, an image is formed by causing an oxidation-reduction reaction in an exposed portion by exposure and heating. The latent image on the silver halide serves as a catalyst, and the organic silver salt reacts with the reducing agent under heating to form an image. It is known to add a toning agent to control the tint of the image area. The toning agent also functions as a development accelerator and is an essential component when a weak reducing agent is used.

However, conventionally known color toning agents are unstable, and if they are made to coexist in the photoconductor, their effects are lost over time, and there is a problem that the image density and photosensitivity after storage are lowered. It was In contrast, US Pat. No. 44
No. 6,648 proposes a method using an acylated phthalazinone. However, the above-described color tone material exhibits its effect over time when stored at room temperature and under high humidity conditions, but the initial color tone effect is not sufficient, the transparency of the photoreceptor after time is poor, and the image There are problems such as inferior homogeneity of parts.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a toning agent having good storage safety, high homogeneity, and excellent image stability. It is what

[0012]

As a result of various investigations, the present inventors have found that certain substituted pyridazine thione compounds are effective as a toning agent for organic silver salts, have a low fog density, and have a fogging density after storage. The present invention was found to give an image having a high image density, leading to the present invention.

That is, the present invention provides an image forming medium characterized in that the recording layer on the support contains at least an organic silver salt, a reducing agent and a pyridazine thione derivative.

Further, the present invention provides an image forming medium in which the pyridazine thione compound is a compound represented by the following general formula (1) or (formula 2).

[0015]

Embedded image (In the general formula (1), R ₁ and R ₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group or a heterocyclic group, and R ₁ and R ₂ are a plurality of carbon atoms. Alternatively, the image forming medium of the present invention may contain at least an organic silver salt, a reducing agent, and a pyridazine thione compound in the recording layer on the support. Alternatively, the recording layer further contains a photosensitive silver halide or a photosensitive silver halide forming agent in addition to the above components. Further, the image forming method of the present invention forms an image on the above image forming medium by imagewise heating, or imagewise exposure and heating.

The present invention will be described in detail below. In the following description, "part" means "part by weight".

The image-forming medium of the present invention has on the support a recording layer containing at least an organic silver salt, a reducing agent, an antifoggant and a toning agent.

In the present invention, a pyridazine thione compound is used as a toning agent. The pyridazinethione compound used in the present invention is pyridazine-3-thione having a substituent at the 5- or 6-position, or both positions, and the two substituents may be the same or different.

The 5- or 6-position substituent is preferably, for example, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, an aralkyl group or a heterocyclic group. As the pyridazine-3-thione used in the present invention, a compound represented by the following general formula (1) (formula 3) is particularly preferable.

[0020]

Embedded image (In the formula (1), R ₁ and R ₂ represent a substituent. In the general formula (1), R ₁ and R ₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group, or It is a heterocyclic group, and R ₁ and R ₂ may be saturated or unsaturated with a plurality of carbon atoms.) The alkyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, such as methyl. And straight chain alkyl groups such as ethyl, propyl, octyl, noryl and behenyl, and branched alkyl groups such as isopropyl, t-butyl, isobutyl and isopentyl.

Preferred substituted or unsubstituted aryl groups are those having 6 to 20 carbon atoms, such as phenyl and
Naphthyl, anthryl, 2-nitrophenyl, 4-nitrophenyl, 2-methylphenyl, 4-methylphenyl, 4-t-butylphenyl, 4-methoxyphenyl,
2-cyanophenyl, 4-cyanophenyl, 3-halogen-substituted phenyl, 4-halogen-substituted phenyl and the like can be mentioned. Here, halogen means chlorine, bromine, or iodine.

Examples of the substituted or unsubstituted aralkyl group include benzyl, naphthylmethyl, 4-methylbenzyl,
4-cyanobenzyl, 4-halogen-substituted benzyl, 4-
Methoxybenzyl, 4-nitrobenzyl and the like can be mentioned.

Examples of the substituted or unsubstituted heterocycle include pyridyl, quinolyl, indoyl, furyl, thienyl, imidazoyl, isothiazoyl, isoxazoyl, pyrazinyl, 4-methylpyridyl, 4-cyanopyridyl, 2
-Methylthienyl, 2-halogen-substituted thienyl, 2-cyanothienyl, 2-methylfuryl, 2-cyanofuryl,
3-halogen-substituted furyl and the like can be mentioned.

When the substituents R ₁ and R ₂ are bound to each other by a plurality of carbon atoms, the carbon number is preferably 3-5.

The pyridazine-3-thione compound used in the present invention can be easily synthesized by reacting the corresponding pyridazine-3-thione compound with a commercially available Lawesson's reagent. Preferred examples of the pyridazine-3-thione compound used in the present invention are shown below, but the invention is not limited thereto.
6-methylpyridazine-3-thione, 6-t-butylpyridazine-3-thione, 6-phenylpyridazine-3-
Thione, 6- (2-pyridyl) pyridazine-3-thione, 6- (3-pyridyl) pyridazine-3-thione, 6
-(1-naphthyl) pyridazine-3-thione, 6- (2
-Thienyl) pyridazine-3-thione, 6- (2-furyl) pyridazine-3-thione, 6-tolylpyridazine-
3-thione, 6- (p-nitrophenyl) pyridazine-
3-thione, 6- (p-cyanophenyl) pyridazine-
3-thione, 6- (2-hydroxyphenyl) pyridazine-3-thione, 5,6-dimethylpyridazine-3-thione, 5-methyl-6-t-butylpyridazine-3-thione, 5-ethyl-6- Methylpyridazine-3-thione, 5-phenyl-6-methylpyridazine-3-thione, 5-methyl-6- (2-thienyl) pyridazine-3
-Thion, 5-methyl-6- (2-furyl) pyridazine-3-thione, 5-methyl-6-ethylpyridazine-3
-Thion, 5,6-diphenylpyridazine-3-thione, 5- (2-furyl) -6-methylpyridazine-3-
Thione, 5,6-di (2-furyl) pyridazine-3-thione, 5,6-di [2- (4-methylfuryl)] pyridazine-3-thione.

Preferred examples of pyridazine-3-thione having a condensed ring are shown below, but the present invention is not limited thereto.

[0027]

[Chemical 4] The toning agent used in the present invention does not decompose even in a severe environment. Therefore, the image forming medium of the present invention gives a good image even after long-term raw storage (preservation in an unused state).

As the organic silver salt, "basics of photographic engineering"
(The Photographic Society of Japan, Corona Co., Ltd., Tokyo, 1st edition, 1
982) Non-silver salt edition P247 and JP-A-59-55
It is possible to use the organic silver salts and triazole silver salts described in JP-A No. 429, etc., and it is preferable to use silver salts having low photosensitivity. For example, it is a silver salt of an aliphatic carboxylic acid, an aromatic carboxylic acid, a thiol, a thiocarbonyl compound having α-hydrogen, and an imino group-containing compound.

As the aliphatic carboxylic acid, acetic acid, butyric acid,
There are succinic acid, sebacic acid, adipic acid, oleic acid, linoleic acid, linolenic acid, tartaric acid, palmitic acid, stearic acid, behenic acid, etc., but generally, the smaller the carbon number, the more unstable the silver salt. Therefore, a compound having an appropriate carbon number (for example, a carbon number in the range of 15 to 28) is preferable.

Examples of the aromatic carboxylic acid include benzoic acid or its derivative, quinolinic acid or its derivative, naphthalenecarboxylic acid or its derivative, salicylic acid or its derivative, gallic acid, tannic acid, phthalic acid, phenylacetic acid or its derivative, and pyrol. There are such as meritic acid.

Examples of the thiocarbonyl compound having thiol or α-hydrogen include 3-mercapto-4-phenyl-1,2,4-triazole, 2-mercaptobenzimidazole, 2-mercapto-5-aminothiadiazole and 2-mercapto. Benzothiazole, S-alkyl thioglycolic acid (alkyl group having 12 to 23 carbon atoms),
Dithiocarboxylic acids such as dithioacetic acid, thioamides such as thiostearoamide, 5-carboxy-1-methyl-2-phenyl-4-thiopyridone, mercaptotriazine, 2-mercaptobenzoxazole, mercaptooxathiazole or 3-amino- 5-benzylthio-
1,2,4-triazole, US Pat.
The mercapto compound described in No. 3,274 can be mentioned.

Examples of the compound containing an imino group include JP-B-44-30270 and JP-B-45-18416.
Benzotriazole or its derivative described in Japanese Patent Publication No.
For example, alkyl-substituted benzotriazoles such as benzotriazole and methylbenzotriazole, halogen-substituted benzotriazoles such as 5-chlorobenzotriazole, carboimide benzotriazoles such as butylcarbimidobenzotriazole, and JP-A-58-118.
No. 6,220,709, such as nitrobenzotriazoles described in JP-A-639, sulfobenzotriazole, carboxybenzotriazole or a salt thereof described in JP-A-58-115638, and hydroxybenzotriazole. Typical examples include 2,4-triazole, 1H-tetrazole, carbazole, saccharin, imidazole and derivatives thereof.

As the reducing agent, all materials (preferably organic materials) capable of reducing silver ions into metal salts can be used. Such reducing agents include monophenols, bisphenols, trisphenols, tetrakisphenols, mononaphthols, bisnaphthols, hydroxynaphthalenes, sulfonamidephenols, biphenols, trihydroxynaphthalenes,
Dihydroxybenzenes, trihydroxybenzenes,
Tetrahydroxybenzenes, hydroxyalkyl monoethers, ascorbins, 3-pyrazolidones, pyrazolones, pyrazolines, sugars, phenylenediamines, hydroxyamines, reductones, hydrooxamic acids, hydrazines, hydrazides, amides Examples thereof include oximes and N-hydroxyureas.
Among these, p-bisphenols, o-bisphenols, bisnaphthols, 4-substituted naphthols and the like are particularly preferable. Further, the reducing agent described in JP-A-3-135564 is also preferably used.

The recording layer preferably contains an appropriate binder for the purpose of improving the coating property and dispersibility thereof. Examples of binders include cellulose esters such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, acetic acid / cellulose propionate, and acetic acid / butyrate cellulose. Ethers of cellulose such as methyl cellulose, ethyl cellulose, propyl cellulose and butyl cellulose; vinyl polymers such as polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol and polyvinyl pyrrolidone; styrene-butadiene copolymer, Styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, etc. Polymers like; polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, acrylic polymers such polyacrylonitrile, polyesters such as polyethylene terephthalate;
Poly (4,4-isopropylidene-diphenylene-co-
1,4-cyclohexylene dimethylene carbonate),
Poly (ethylenedioxy-3,3'-phenylene thiocarbonate), poly (4,4'-isopropylidene-diphenylene carbonate-co-terephthalate), poly (4,4-isopropylidene-diphenylene carbonate), Poly (4,4'-sec-butylidenephenylene carbonate), poly (4,4'-isopropylidene-
Polyphenylene polymers such as diphenylene carbonate-block-oxyethylene); polyamides; polyimides; epoxy polymers; phenolic polymers;
Polyolefins such as polyethylene, polypropylene and chlorinated polyethylene; and natural or synthetic resins such as gelatin. In particular, polyvinyl acetals such as polyvinyl butyral and polyvinyl formal, and vinyl copolymers such as vinyl chloride vinyl acetate copolymer are preferable.

The preferred blending ratio of each component in the image forming medium of the present invention is as follows. The content of the organic silver salt is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, and particularly preferably 20 to 50% by weight based on the recording layer. Even when the recording layer is composed of multiple layers as described later, the content of the organic silver salt is the above value for all recording layers. The content of the reducing agent is preferably 0.05 to 3 mol, and more preferably 0.2 to 2 mol, based on 1 mol of the organic silver salt. The content of the pyridarinthione compound is 0.01 mol to 2 mol, preferably 0.05 mol to 0.9 mol, relative to 1 mol of the organic silver salt. The amount of the binder contained, if necessary, is 0.5 to 10 parts by weight, more preferably 0.5 to 1 part by weight of the organic silver salt.
A proportion of ˜5 parts by weight is preferred.

To further improve the sensitivity and image quality, a photosensitive silver halide may be contained in the recording layer so that writing can be performed by light. Examples of the photosensitive silver halide include silver chloride, silver bromide, silver chlorobromide, silver iodobromide, silver chloroiodobromide and the like.

As a method for preparing these silver halides, a part of the silver oxide compound is halogenated with a photosensitive silver halide-forming component such as ammonium bromide, lithium bromide, sodium chloride, N-bromosuccinimide or the like. And a so-called external silver halide is contained.

Examples of the crystal shape of these silver halides include cubic, octahedral and tabular ones, but cubic and tabular silver halides are particularly preferable. The length of one side of the cubic silver halide crystal is preferably 0.01 to 2 μm, more preferably 0.02 to 1.3 μm. These silver halides may be subjected to chemical sensitization as is done for ordinary photographic emulsions. That is, sulfur sensitization, noble metal sensitization, reduction sensitization and the like can be used.

The silver halide crystal surface layer may contain iridium ions. The crystal surface layer is a layer from the crystal surface of silver halide to a predetermined depth. In this case, the crystal form of silver halide is (1, 0,
The tetragonal form of the 0) plane is preferred. One side of the silver halide grain is preferably 0.001 μm to 1.0 μm, more preferably 0.01 μm to 0.2 μm, and 0.03 μm.
Particularly preferred is μm to 0.1 μm. The thickness of the crystal surface containing indium ions is 10 times the length of one side of the crystal.
% Or less, and more preferably 5% or less. The crystal surface layer containing iridium ions preferably has a crystal surface layer containing iridium ions at 0.5% or more of the length of one side of the crystal.

In order to adjust the silver halide containing iridium ions, an iridium ion supplier may be added when silver halide is produced from the reducible organic silver salt and the silver halide-forming component. As the iridium ion supplier, for example, iridium tetrachloride, iridium (IV) hexachloride potassium, iridium (IV) hexachloride sodium and the like are preferable.

In order to make the silver halide crystal surface layer contain iridium ions, an iridium ion donor may be introduced after a short time has elapsed from the start of silver halide production. For example, silver halide is 90% by weight of the specified amount
It is sufficient to start feeding the iridium ion supplier at the time of generation.

All of the silver halide used in the present invention are
Although it may contain iridium ions, it may be a mixture of silver halides containing iridium ions and silver halides not containing iridium ions.

The content of iridium ion in the photosensitive layer is
1 × 10 per mol of total halogen silver contained^-8~ 1 x 1
0^-FourMolar is preferable, and more preferably 1 × 10.^-7~ 1x
10 ^-6A molar ratio is preferred.

Further, these silver halides may have a multiple structure in which the halogen composition in the grain is uniform or different, and two or more kinds of silver halides having different halogen composition, grain size, grain size distribution, etc. You may use together.

The preferable content of the photosensitive silver halide, which is optionally contained, is 0.001 to 1 mol per mol of the organic silver salt.
2 mol, especially 0.05 to 1 mol is preferred.

A photosensitive silver halide forming agent (for example, a halogen compound such as tetrabutylammonium bromide, N-bromosuccinimide, bromine or iodine) may be used in place of the photosensitive silver halide, in which case silver halide formation is carried out. The content of the agent can be considered as in the case of silver halide.

The recording layer may contain a sensitizing dye such as a cyanine dye or a merocyanine dye. When a sensitizing dye is contained, the content is 1 × 10 ^-7 to 1 per mol of the organic silver salt.
× 10 ^-2 mol is preferable.

In the present invention, various compounds can be added to the recording layer. The image forming medium of the present invention may contain a toning agent, if necessary. Examples of the color toning agent include phthalazinone or a derivative thereof described in US Pat. No. 3,080,254, JP-A-46-6.
No. 074, the cyclic imides described in JP-A-50-32
The phthalazinone compound described in Japanese Patent No. 927 can be mentioned.

The image-forming medium of the present invention may contain an organic acid, if necessary, in order to improve the color tone of the image and the stability after the image formation. Particularly, a long-chain fatty acid is used alone or in combination. It is preferably contained.

The image forming medium of the present invention may contain an anti-coloring agent, if necessary, in order to prevent coloring of the non-image area due to light after image formation. Examples of the coloring preventing agent include compounds described in JP-A-61-1296642, for example, α, α-dibromoacetophenone, α, α, P-tribromoacetophenone, α, α-.
Examples thereof include dibromo-P-acetophenone and α, α-dibromo-o, p-dichloroacetophenone.

The image forming medium of the present invention may further contain a development accelerator, if necessary. Preferred development accelerators include alkali metal salt compounds of fatty acids described in JP-B No. 64-8809.

The image forming medium of the present invention may contain an antistatic agent, if necessary. As an antistatic agent,
A fluorinated surfactant can be used, or a combination of a fluorinated surfactant and a nonionic surfactant described in JP-A No. 64-24245 can be used.

In the image forming medium of the present invention, if necessary, an ultraviolet absorber, an anti-irradiation dye, a matting agent,
A fluorescent whitening agent or the like can be contained.

In the image forming medium of the present invention, if necessary, an N-haloamide compound described in JP-A-49-90118, a sulfinic acid or a salt thereof described in JP-A-50-123331, and JP-A- 2-Thiouracils described in JP-A-51-3223, rosins and terpenes described in JP-A-51-57435, oxazoline compounds described in JP-A-51-2431, and JP-A-51-122.
Other thermal antifoggants such as benzotriazoles and benzenethiosulfonic acids described in JP-A No. 430, and mercaptotetrazoles described in JP-A No. 51-6016 may be contained.

Examples of the support include synthetic resin films such as polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, and cellulose acetate, synthetic paper, paper coated with synthetic resin films such as polyethylene, art paper, photographic bariter paper, and the like. Examples thereof include papers, a metal plate (foil) such as aluminum, a synthetic resin film having a metal vapor deposition film, or a glass plate.

A protective layer is optionally provided on the heat-sensitive recording layer in order to increase the transparency of the image forming medium, increase the image density, improve the raw storability and, in some cases, the heat resistance of the image forming medium. Can be provided. The suitable thickness of the protective layer is 1 to 20 μm. If it is thinner than this, the above effects are lost, and if it is too thick, there is no special advantage and only the cost is increased. The polymer used for the protective layer is preferably heat resistant, colorless, and easily soluble in a solvent, for example, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer (preferably 50 mol% vinyl chloride). Above), polyvinyl butyral, polystyrene, polymethyl methacrylate, benzyl cellulose, ethyl cellulose, cellulose acetate butyrate, cellulose diacetate, cellulose triacetate,
Polyvinylidene chloride, chlorinated polypropylene, polyvinylpyrrolidone, cellulose propionate, polyvinyl formal, polycarbonate, cellulose acetate propionate, gelatin, gelatin derivatives such as phthalated gelatin, acrylamide polymer, polyisobutylene, butadiene-styrene copolymer (any (Monomer ratio), polyvinyl alcohol, etc. can be mentioned.
In addition to these binders, colloidal silica may be contained in the protective layer.

Preferred polymers for the protective layer are those having a heat resistance of 115 ° C. or higher and a bending ratio of 1.45 or higher at 20 ° C.

In the image forming medium of the present invention, a recording layer can be formed on the support as a single layer or multiple layers. When the recording layer has a multilayer structure, it is preferable that the recording layer has a layer containing an organic silver salt and an antifoggant and a layer containing a reducing agent.

When each layer having various functions such as a recording layer and a protective layer is separately formed in the image forming medium of the present invention, each of these layers can be coated by various coating methods. Examples of the method for forming each layer include a dipping method, an air knife method, a curtain coating method, a gravure coating method, a doctor coating method, and US Pat. No. 2,681,294.
There is an extrusion coating method using a hopper described in the specification. If desired, two or more layers can be coated simultaneously.

Next, a method of forming an image using the image forming medium of the present invention will be described. When the image forming medium of the present invention is imagewise heated by using a thermal head or a laser beam, an oxidation-reduction reaction proceeds to form an image. The energy amount of the laser beam is preferably 0.5 mJ / cm ² or more on the medium surface. The heating temperature by the thermal head is 140 to 250 ° C, and further 150 to 22
0 ° C is preferred. The heating time by the thermal head is 0.
01 to 2 seconds is preferable.

When an image is formed using a laser beam, the image forming medium of the present invention may contain a photothermal conversion material that efficiently converts light energy into heat energy. As such a light-heat conversion material, for example, inorganic metals or organic facial dyes are preferable, and a wavelength of 600 n is particularly preferable.
Those that absorb light of m or more are preferable.

As the inorganic metals used for the photothermal conversion material, carbon black, silicate, etc. are preferable.
Examples of organic facial dyes include polymethine dyes, azulene dyes, pyrylium dyes, merocyanine dyes, cyanine dyes, rhodamine dyes, naphthoquinone dyes, phthalocyanine dyes, fluorene dyes, aluminum dyes, diimonium dyes, azo pigments, perylene pigments, metal chelate compounds. Etc. are preferred.

When the photothermal conversion material is contained, the content of the photothermal conversion material is preferably 0.1 to 30% by weight based on the recording layer.

On the other hand, the image forming medium of the present invention containing a silver halide or a silver halide forming component exhibits good photosensitivity and heat developability. That is, for the image forming medium of the present invention,
When exposure according to a desired image is performed with an appropriate light source, silver nuclei are first generated to form a latent image. Further, if this is appropriately heated, an image corresponding to the image exposure is developed by the redox reaction. As the light source in this case, for example, a semiconductor laser or LED light can be used.
The exposure speed is 1 × 10 ⁻³ sec / dot to 1
Even if the exposure time is up to × 10 ^-7 sec / dot, a practical optical density can be obtained without causing reciprocity law failure, but front sub-exposure or post-sub-exposure may be performed as necessary.

There are various means for heat-developing the image forming medium of the present invention containing a silver halide or a silver halide-forming component. For example, the photoreceptor may be brought into contact with a simple heating plate or a heated drum. May be brought into contact with, or may be passed through a heated space in some cases. Moreover, you may heat by a high frequency heating or a laser beam. The heating temperature is 70 to 160 ° C, and further 90 to
150 ° C is suitable, and more preferably 100 to 140
° C. By extending or shortening the heating time,
It is possible to perform heat development at a higher or lower temperature within the above temperature range. The development time is usually 1-60 seconds, preferably 3-20 seconds. Since the heat development is performed with low energy, the unexposed area is not discolored.

[0066]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Polyethylene terephthalate (PET) having a thickness of 25 μm
The film was used as a support. An aluminum layer having a thickness of 0.1 μm was formed on this support by vacuum vapor deposition. Then, 50 parts of methyl ethyl ketone, 50 parts of toluene and a vinyl chloride-vinyl acetate-maleic acid copolymer (manufactured by Zeon Corporation) on the aluminum layer.
A solution of 5 parts was dried using a wire bar to give a dry coating film of 0.
The primer layer was formed by coating so as to have a thickness of 5 μm. Furthermore, a solution having the following composition on this primer layer,
A recording layer was formed by adding 1.5 parts of a 10% by weight acetone solution of 6-methylpyridazine-3-thione so that the amount of silver per 1 m ² was 2.4 g. Silver behenate 1.0 part Behenic acid 0.5 part 2,2′-methylenebis (6-t-butyl-4-methylphenol) 1.0 part Vinyl chloride-vinyl acetate copolymer 2.5 parts 1,3 -Pentadiene copolymer 0.2 parts Tetrahydrofuran 12.0 parts Further, a 10% ethyl acetate solution of vinyl acetate (number average degree of polymerization: 5000) was applied on the recording layer so as to have a dry film thickness of 1 μm to form a protective layer. An image forming medium of the present invention was obtained.

The image-forming medium thus obtained was recorded by a heat-sensitive evaluation machine (TH-PMD manufactured by Okura Electric Co., Ltd.), and the optical densities of the heated portion and the non-heated portion were measured by a Macbeth densitometer (Macbeth RD-914 type). It was measured at. The optical density measurement is
Immediately after creating the image forming medium, and after creating 50
The test was performed for 72 hours (raw storage test) in an environment of 80 ° C and 80% RH. A voltage was applied to the thermal head of the heat-sensitive evaluation machine under the condition of 24 V-2 msec. The measurement results are shown in Table 1. The image-forming medium obtained as described above is placed in a place exposed to direct sunlight without recording.
After leaving for one day, the degree of discoloration of the image forming medium was measured by the above Macbeth densitometer (light resistance test). Table 1 shows the measurement results.
It was shown to.

Examples 2, 3 and Comparative Example 1 An image forming medium was prepared in the same manner as in Example 1 except that the following compounds were added in place of 6-methylpyridazine-3-thione of Example 1. Examples 2, 3). In addition, as a comparative example, an image forming medium was prepared in which 2-acetylphthalazinone was added and the other conditions were the same as those of the example (Comparative Example 1). [Example 2] 6- (2-thienyl) pyridazine-3-thione [Example 3] 6- (2-furyl) pyridazine-3-thione The same measurement as in Example 1 was carried out for each image-forming medium thus obtained. went. The measurement results are shown in Table 1.

[0070]

[Table 1] Example 4 An image forming medium of the present invention was obtained in the same manner as in Example 1 except that 0.5 part of the following photothermal conversion material was added to the coating liquid for the recording layer prepared in Example 1.

[0071]

Embedded image The thus obtained image forming medium was recorded with a semiconductor laser having a wavelength of 780 nm, and the optical density of the heated portion and the non-heated portion was measured in the same manner as in Example 1. The exposure speed of the semiconductor laser was 1 msec / dot. The energy of the semiconductor laser is 50 mJ / on the surface of the image forming medium.
It was set to mm ² . The measurement results are shown in Table 2. A light resistance test was conducted on this image forming medium in the same manner as in Example 1. The results are shown in Table 2.

[0072]

[Table 2] Example 5 A light and heat sensitive composition having the following composition was prepared under safe light. Polyvinyl butyral 5.0 parts Silver behenate 2.5 parts Behenic acid 2.0 parts Silver bromide 0.2 parts 2,2'-Methylenebis (6-t-butyl-4-methylphenol) 1.0 part Xylene 30 Parts n-Butanol 30 parts The above silver bromide is a cubic crystal having a crystal fraction index of [100], and the average length of one side of the crystal is 0.07 μm. To this composition was added 0.21 part by weight of 6-methylpyridazine-3-thione to obtain a PE having a thickness of 25 μm.
A T film was coated on a support to a dry film thickness of 10 μm to form a recording layer, and a protective film of 2 μm was formed on the recording layer.
m polyvinyl alcohol layer was applied to obtain an image forming medium of the present invention.

The image forming medium thus obtained was irradiated with light using a tungsten light source. Light irradiation was performed through a mask with an exposure amount of 15000 lux seconds.

With respect to the image forming medium on which an image was thus formed, the optical densities of the exposed portion and the unexposed portion were measured using a transmission / reflection chromaticity meter (NLM-STD-Tr manufactured by Narumi Shokai). The optical densities were measured immediately after the image forming medium was prepared and after being prepared for 72 hours in an environment of 50 ° C. and 80% RH (raw preservation test). The measurement results are shown in Table 3. The image-forming medium obtained as described above was placed under a fluorescent lamp for 1 hour without recording, and the degree of discoloration of the image-forming medium was measured by the above-mentioned optical density with a transmission / reflection chromaticity meter ( Light resistance test). Table 3 shows the measurement results
It was shown to.

Examples 6 and 7 Instead of 6-methylpyridazine-3-thione of Example 5, 5,6-dimethylpyridazine-3-thione (Example 6) and 6-t-butylpyridazine-3-thione (Example 7) An image forming medium was prepared in the same manner as in Example 5, except that. The results of evaluating the obtained image-formed body in the same manner as in Example 5 are shown in Table 3.

Comparative Examples 2 and 3 As Comparative Example 2, an image forming medium was prepared in the same manner as in Example 5 except that 6-methylpyridazine-3-thione was not added. As Comparative Example 3, an image forming medium was prepared in the same manner as in Example 5, except that 4.5 parts of 2-acetylphthalazinone (10 wt% acetone solution) was added instead of 6-methylpyridazine-3-thione. The results of evaluating the obtained image-formed body in the same manner as in Example 5 are shown in Table 3.

[0077]

[Table 3]

[0078]

When the image forming medium of the present invention is used, the image density is high, the image forming medium is excellent in raw storage stability, and is excellent in suppressing printing (discoloration) due to fog and light.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B41M 5/18 101R 101C (72) Inventor Motokazu Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tetsuro Fukui 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. An image forming medium characterized in that a recording layer on a support contains at least an organic silver salt, a reducing agent and a pyridazine thione derivative. 2. The image forming medium according to claim 1, wherein the pyridazine thione compound is represented by the following general formula (1) (formula 1). Embedded image (In the general formula (1), R ₁ and R ₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group or a heterocyclic group, and R ₁ and R ₂ are a plurality of carbon atoms. Alternatively, it may be a saturated bond or an unsaturated bond with a heteroatom or both. 3. The image forming medium according to claim 1, wherein the recording layer further contains a photosensitive silver halide and / or a photosensitive silver halide forming agent. 4. An image forming method, which comprises heating the image forming medium according to claim 1, 2 or 3 into an image to form an image. 5. An image forming method comprising forming an image by performing image exposure and heating on the image forming medium according to claim 1.